The present invention relates to a magnetic bubble memory device and, more specifically, to a bubble device with a current stretcher detector and a method of detection for this type of bubble device.
There is known an ion-implanted bubble device having a contiguous propagation pattern made by using an ion-implantation technique. Bubbles are written in the propagation pattern, with one for every bit or at least one bit apart, and moved successively bit by bit in response to a rotating drive field.
On the other hand, there is known a current stretcher detector, which includes a stretch conductor associated with a propagation pattern of a bubble device and operative, when applied with a stretch current, to stretch a bubble which reaches the detection position, and also includes a detecting element utilizing a magnetoresistance effect. This stretcher detector is principally used in the ion-implanted bubble device, but also can be used in a familiar Permalloy bubble device. The detection of bubbles by this stretcher detector is performed by applying a stretch pulse current to the stretch conductor in conjunction with the drive field, so as to stretch a bubble which reaches the detection position, and the stretched bubble can also be detected by the detecting element.
However, in a conventional detection method, a stretch pulse current is applied to every cycle of the drive field. Accordingly, there is a problem in that the efficiency of detection at a high frequency, for example 300 KHz, is low, as will be described in detail hereinafter.
Moreover, a conventional bubble device with a current stretcher detector has various problems in certain characteristics, which also will be described in detail hereinafter.